1. Field of the Invention
The present invention relates to components for medical breathing circuits and in particular to a humidifying apparatus to aid in the delivery of pressurised oxygen and/or air to a patient.
2. Summary of the Prior Art
A number of methods are known in the art for assisting a patient's breathing. Continuous Positive Airway pressure or CPAP involves the administration of air under pressure to a patient. It is used in the treatment of snoring and Obstructive Sleep Apnoea (OSA), a condition characterised by repetitive collapse of the upper airway during inspiration. Positive pressure splints the upper airway open, preventing its collapse. Treatment of OSA with CPAP has proven to be both effective and safe. Typically included within a CPAP device is a humidifier to humidify the air supplied to the patient, a blower to generate a positive air pressure, and a water reservoir to provide a constant supply of water to the humidifier.
For devices that use high humidity, e.g. 44 mg delivery, at relatively high flow rates, e.g. 40 litres per minute, it is preferable to use auto feed chambers that are filled from a reservoir. Common prior art devices of this type are shown in FIG. 1; these are normally used in a hospital environment but can be also used in a home environment. In particular these devices use a water reservoir 1 located above a humidification chamber 2. As the water supplied to the humidification chamber 2 is gravity fed, the water reservoir must be mounted above the humidification chamber 2 in order to create a suitable pressure differential for flow to occur. In some instances locating a reservoir above the humidification chamber 2 at a point that provides adequate pressure differential for flow to occur may not be practical (for example, if the required mounting is higher than the ceiling due to the high pressure created by the system) or is awkward as typically this is where other medical devices are located, for example drug supplies for intravenous drips.
Non-medical use humidifiers are known to have various water feeds, such as that in U.S. Pat. No. 3,801,077 and U.S. Pat. No. 4,913,140 that have a water tank or chamber that includes water feeds such that the level of the water within the tank or chamber is controlled by a float.